1. Field of the Invention
The present invention relates to a camera including a large capacity memory rewritable from outside.
2. Related Background Art
With an advancement of an electronic camera, a high-function microcomputer (hereinafter simply termed a CPU) has hitherto performed processing in order to execute an auto exposure, focusing, a feed of a film and electronic flash control.
Take the auto exposure for example, and the explanation goes as follows. To start with, there is read an object luminance signal from a light metering sensor incorporated into the camera and a sensitivity signal of the film loaded therein. A calculation of values thereof is executed based on an arithmetic method stored beforehand in a ROM, thereby obtaining a proper exposure condition. Then, a photographer is notified of a result of this by outputting a signal to a display unit provided outwardly of the CPU. Further, when depressing a shutter button, a control signal is transmitted to an external actuator so that a stop value of a lens and an aperture time of a shutter are obtained as indicated by the arithmetic result.
As well known, such a CPU is of a so-called one-chip type, and the interior thereof is provided with an I/O control unit, a read-only memory (hereinafter abbreviated to a ROM) for storing a processing content and a processing sequence, a random access memory (hereinafter abbreviated to a RAM) for temporarily storing inputted signals and a logic unit for executing calculations.
As well, the ROM (referred to as a mask ROM) in the CPU is manufactured in accordance with a processing program in a mask step of its manufacturing process, and hence it is absolutely impossible to make a change after being manufactured. If a mistake in the processing program is found out, or if a higher degree of arithmetic program corresponding to a sensor exhibiting a higher performance is to be used, or if the processing program is changed for such a reason that a specification of the actuator is modified, the CPU itself is newly remanufactured before the manufacturing process, and, further, the CPU has to be re-mounted on a circuit board within the camera by soldering.
Also, a so-called one-time CPU transiently employed at an initial stage of the product such as a trial product does not have to undergo the manufacturing process as in the case of a mask ROM because of being electrically rewritable to the internal ROM. It is impossible, though there exists the potential that the processing program can be confirmed at an early stage, to erase the written processing program a just as it is impossible to do so in the mask ROM and to perform a repetitive usage. Besides, the remounting by soldering is also needed.
On the other hand, a flash memory (hereinafter abbreviated to an FM) has been developed in recent years. The FM is similar to an EEPROM wherein electrical writing and erasing processes can be repeatedly performed. However, an internal structure thereof is simple, and, hence, a large-capacity memory can be formed on a small chip. Then, a storage on the order of several tens or more of kilobytes as in the processing program for indicating the operation of the CPU is conceived easily.
As explained above, there is the purpose for enhancing the performance in the camera, but, nevertheless, there still exists a problem such that it is impossible to quickly change the processing program within the ROM.